JPH08213846A - Method for correcting distortion of modulation wave and transmitter - Google Patents

Abstract

PURPOSE: To correct the distortion of a modulation wave. CONSTITUTION: A signal processing section 3 applies digital signal processing to transmission information to provide the output of two couples of base band signals, a quadrature modulation section 7 converts a carrier into two signals with a prescribed phase difference and they are respectively multiplied with a couple of the above base band signals and the products are added and a modulation wave is outputted. In this case, a branching section 4 provided between the quadrature modulation section 7 and an output section 5 provides properly a modulation wave outputted from the quadrature modulation section 7 to the output section 5 and a detection section 6. Then the detection section 6 detects the modulation wave to provide the output of an envelope signal being a signal of the envelope of the modulation wave and a control section 32 provides the output of a distortion correction signal to a signal processing section 3 so as to minimize the amplitude fluctuation of the envelope signal thereby correcting distortion of the modulation wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of correcting distortion of a modulated wave in a transmitter and a transmitter using the method, and more particularly, to detecting distortion information of a modulated wave and using the basic signal for generating the modulated wave based on the information. The present invention relates to a distortion correction method for a modulated wave that corrects the distortion by correcting a certain baseband signal, and a transmitter using the method.

[0002]

2. Description of the Related Art Generally, a narrow band modulation system is adopted in a transmission device such as a digital cellular automobile telephone in order to effectively use a frequency. The narrow band modulation method includes an I baseband signal (hereinafter, I signal [In-phas
e]) and a Q baseband signal (hereinafter, Q signal [Qua
The quadrature modulation method using the (dary] is often used.

FIG. 2 is a block diagram showing a general circuit configuration of a transmission device which performs a signal processing on transmission information such as voice data to generate a modulated wave. The audio data is arithmetically processed by a digital signal processor (DSP) 110 to become I and Q signals, which are analogized by a D / A converter 111. Then, after the unnecessary signal is removed by the filter 112, the signal is input to the quadrature modulator 105 and a modulated wave is output. The DSP 110 and the D / A converter 111 are
It is controlled by the control unit (CPU) 115. FIG. 3 shows a detailed block diagram of the quadrature modulator 105, in which the quadrature modulator 105 includes first and second multipliers 101 and 10.
It has a 2, 90-degree phase shifter 103 and an adder 104. Then, at the connection point between the first multiplier 101 and the 90-degree phase shifter 103, the carrier wave is input from the carrier wave oscillator 109 and input to the first multiplier 101, and the 90-degree phase shifter 103 shifts the phase to 90 degrees. The second multiplier 102
To enter.

The first multiplier 101 is provided with an input terminal 106 for inputting an I signal, and the second multiplier 102 is provided with an input terminal 107 for inputting a Q signal. As a result, the first multiplier 101 multiplies the I signal by the carrier, and the second multiplier 102 multiplies the Q signal by the carrier. Then, the first and second multipliers 101 and 102
The outputs from are added by the adder 104 to generate a modulated wave, and the modulated wave is output from the output terminal 108.

The I and Q signals are obtained by performing appropriate code processing (mapping) and band limitation on the data to be transmitted, and various modulated waves can be obtained depending on the code processing method. For example GMSK in GSM in Europe
Modulation method and π for digital cellular in North America and Japan
/ 4DQPSK modulation method and the like.

FIG. 4 (a) is a signal point diagram for the QPSK modulation system and FIG. 4 (b) is a signal point diagram for the π / 4 shift QPSK modulation system. Values taken by the orthogonal I-axis and Q-axis signals are shown. Is determined by the information dibit to be transmitted. In the signal point diagram, the distance from the origin (the center of the signal point diagram) to the signal point represents the amplitude of the modulated wave.

In the signal point diagram shown in FIGS. 4 (a) and 4 (b), when the signal point is first located at point a, if the next information dibit is "10", the phase shifts from point a to point b. , "0
If it is "0", the phase shifts from the point a to the point c. It should be noted that when the phase shifts to point c, it passes through the origin in the QPSK modulation method, but does not pass through the origin in the λ / 4 shift QPSK modulation method.

[0008]

However, in the above-mentioned transmitting apparatus, (1) when there is a carrier leak in the quadrature modulator 105, (2) there is an imbalance in the amplitudes of the I and Q signals input to the quadrature modulator 105. In such a case, (3) there is a problem that a modulated wave, which will be described later, is distorted when an accurate degree of quadrature cannot be obtained when the phases of carriers are orthogonalized by the 90-degree phase shifter 103.

This problem will be described with reference to FIG. Figure 6
(a) is a signal point diagram in an ideal system, Fig. 6 (b) is a signal point diagram in a system with carrier leakage, and Fig. 6 (c) is I, Q.
A signal point diagram in a system where the signal amplitude is unbalanced (I signal <Q signal), and FIG. 6D shows a signal point diagram in a system in which the orthogonality of carrier waves is not accurate. In FIG. 6, x indicates an actual signal point, and ⊚ indicates an ideal signal point.

(1) Distortion of modulated wave when quadrature modulator has carrier leak Generally, the circuit used for the first and second multipliers 101 and 102 is a balanced cross-coupling type as shown in FIG. It is composed of a differential stage (Gilbert cell). As shown in the figure, since the circuit is provided with a plurality of elements such as transistors in a symmetrical configuration, if there is an imbalance in the element characteristics, the output will be different even if the same signal is input.

Therefore, even if the I and Q signals with the amplitude "0" are input, if the device characteristics such as the transistor are uniform,
Since the carrier wave suppression function works, the carrier wave is not output.
However, if the element characteristics are not uniform, the carrier leaks to the output, a phenomenon called carrier feedthrough occurs, and carrier leakage of the quadrature modulator 105 appears.

Therefore, as shown in FIG. 6 (b), each signal point is uniformly displaced in the leak direction. Figure 6 (b) shows the first and second
The case where there is a carrier leak in both the multipliers 101 and 102 is shown. That is, a circle in which signal points are lined up (hereinafter, this circle is referred to as a signal circle) has its origin O changed to O ′ without losing its shape, and becomes a modulated wave distorted by the amount of the change. Since such a carrier leak becomes remarkable in the microwave band, it becomes a serious problem in a transmitting device such as an automobile telephone used in the band of 800 MHz or more.

(2) Distortion of modulated wave when amplitudes of I and Q signals input to the quadrature modulator are unbalanced Even when amplitudes of I and Q signals input to the quadrature modulator are unbalanced, Distortion occurs in the modulated wave, and causes thereof include variations in conversion gain in the first and second multipliers 101 and 102, variations in conversion gain in the D / A converter 111, variations in gain in the pair of filters 112, and the like.

The variations in the conversion gains of the first and second multipliers 101 and 102 appear remarkably at high frequencies, so that the I and Q signals of the I and Q signals in the high frequency band of the above-mentioned transmitter such as a car telephone set. Amplitude variation becomes large.

Further, even if the I and Q signals having the uniform amplitude are input from the DSP 110, if the conversion gain in the D / A converter 111 varies, the I signal and the Q signal cannot be converted uniformly. An imbalance occurs in the amplitude of the I and Q signals.

Therefore, even if the carrier leak as described in (1) does not exist in the quadrature modulator 105, the signal amplitude itself input to the quadrature modulator 105 already has variations. As a result, a distorted modulated wave is output.

The signal circle in such a case becomes an ellipse as shown in FIG. 6 (c). FIG. 6 (c) shows a case where the Q signal is more unbalanced than the I signal,
In the opposite case, the ellipse has a major axis in the I-axis direction. In any case, since the shape is deformed as compared with that in FIG. 6A, the modulated wave is distorted by this amount.

(3) Distortion of modulated wave when 90 degree phase shifter cannot obtain accurate orthogonality when the phases of carriers are orthogonalized. Various configurations have been proposed as the 90 degree phase shifter 103. In any of the methods, it is technically difficult to maintain the orthogonality over a wide frequency band. Therefore, the orthogonality cannot be maintained depending on the frequency. Therefore, even if there is no imbalance in the amplitudes of the I and Q signals input to the quadrature modulator 105, the modulated wave is distorted. In this case,
As shown in (d), the signal circle is an ellipse because the major and minor axes are not orthogonal.

[0019]

In order to solve the above problems, the present invention provides a method for correcting distortion of a modulated wave according to the first invention, in which transmission information is subjected to digital signal processing
In a method of generating a modulated wave, which outputs a pair of baseband signals, multiplies each of the baseband signals by two carriers orthogonal to each other, and then adds them to generate a modulated wave, when correcting distortion of the modulated wave. Based on the pair of baseband signals,
Generating a constant envelope in the modulated wave, envelope-detecting the modulated wave to obtain an envelope signal, and correcting at least one baseband signal so as to minimize the amplitude fluctuation of this envelope signal, Is characterized by.

The transmitting device according to the second aspect of the present invention, a signal processing unit for digitally processing transmission information to output a pair of baseband signals, and two orthogonal carrier waves and the baseband signal are multiplied. In a transmitter having a quadrature modulator that outputs the modulated wave by adding after performing the above, the envelope detection is performed on the modulated wave formed based on the pair of baseband signals that generate a constant envelope in the modulated wave. A detection unit and a control unit that outputs a distortion correction signal to the signal processing unit based on the envelope signal from the detection unit to correct at least one baseband signal so as to minimize amplitude fluctuation of the envelope signal. And having.

[0021]

According to the first aspect of the present invention, when the distortion of the modulated wave is corrected, a constant envelope is generated in the modulated wave based on the pair of baseband signals. Then, this modulated wave is subjected to envelope detection to obtain an envelope signal.

Since an ideal modulated wave is a state in which there is no amplitude fluctuation of the envelope signal, information on the amplitude fluctuation of the envelope signal is fed back to change either one of the baseband signals, whereby the amplitude of the envelope signal is changed. The distortion of the modulated wave is corrected by minimizing the fluctuation.

According to a second aspect of the invention, the detecting section detects the modulated wave of the baseband signal to obtain an envelope signal.

Then, the control section detects this, and in order to minimize the amplitude fluctuation of the envelope, an amplitude balance control signal for controlling the imbalance of the amplitudes of the two pairs of baseband signals, and a phase difference between the two carriers. Orthogonality control signal for controlling the amplitude of each baseband signal so as to be a modulated wave equivalent to the modulated wave in the case of 90 degrees, and a DC offset balance control for controlling a DC offset value of one of the paired baseband signals. The control unit outputs the distortion correction signal including at least one of the signals to the signal processing unit. The signal processing unit corrects the baseband signal according to the signal, thereby correcting the distortion of the modulated wave.

[0025]

【Example】

<Embodiment of the First Invention> An embodiment of the first invention will be described with reference to the drawings. As described above, the distortion of the modulated wave is caused when (1) there is a carrier leak in the quadrature modulator, (2) when there is an imbalance in the amplitudes of the I and Q signals input to the quadrature modulator,
(3) This occurs when an accurate degree of quadrature cannot be obtained when the phases of carrier waves are made orthogonal by the 90-degree phase shifter.

Then, a method of correcting these distortions will be described. FIG. 7 (a) shows a signal point diagram when no modulation is performed, and I =
The amplitude is normalized such that 0 and Q = 1, and the signal point is fixed to point A.

On the other hand, if the frequency of the carrier wave shifts,
As shown in Fig. 7 (b), the signal point rotates on the signal circle at a constant speed. For example, if the frequency of the carrier wave is shifted by 1000 Hz, the signal point rotates at 1000 rotations / second. Therefore, if the frequency is 1 MHz, it will be 1.00 depending on the direction of rotation.
It becomes a carrier wave of 1 MHz or 0.999 MHz. When the signal point rotates on the signal circle at a constant speed, the frequency is f = 1000 Hz and I = sin (2πft),
It is obtained by Q = cos (2πft). In the signal point diagram, the distance from the origin to the signal point is the amplitude of the modulated wave, that is, the envelope signal, so that the envelope signal is constant when rotating on a perfect circle signal circle.

Therefore, when the amplitudes of the I and Q signals are unbalanced as shown in FIG. 7 (c), the envelope signal varies with the rotation of the signal point. For example, when rotating at a speed of 1000 Hz, the modulated wave becomes as shown in Fig. 7 (d),
The amplitude will change in a cycle of 1/2000 seconds.

FIG. 7 (d) shows a modulated wave when the amplitudes of the I and Q signals are unbalanced. The quadrature modulator 2
If there is a carrier leak in No. 4 or if a correct degree of quadrature cannot be obtained when the phases of the carrier waves are made orthogonal by the 90-degree phase shifter, a modulated wave whose amplitude fluctuates similarly is obtained.

Therefore, when the distortion of the modulated wave is corrected, a constant envelope is generated in the modulated wave based on the pair of baseband signals. Hereinafter, such a signal is appropriately referred to as a test signal. Then, this modulated wave is subjected to envelope detection to obtain an envelope signal. The state where there is no amplitude fluctuation of the envelope signal is an ideal modulated wave, so information is fed back to change the test signal,
As a result, the distortion of the modulated wave is corrected by minimizing the amplitude fluctuation of the envelope signal. A specific example of the method for correcting the distortion of the modulated wave will be described in detail in the following Embodiment 1 of the second invention.

<First Embodiment of the Second Invention> A first embodiment of the second invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a transmission apparatus using the method for correcting distortion of a modulated wave according to the first invention. In the embodiment of the first aspect of the invention, the baseband signal that causes the modulated wave to have a constant envelope is defined as a test signal. The second invention basically follows this definition, but for convenience of description, it may be referred to as a baseband signal, an I signal, or a Q signal as appropriate.

The transmitting device 2 according to the first embodiment multiplies the I signal and the Q signal by a signal processing unit 3 which processes the transmission information into a digital signal and outputs an analog I signal and a Q signal by mutually orthogonal carrier waves. , A quadrature modulator 7 for adding each of them and outputting a modulated wave, an output unit 5 for amplifying the modulated wave and emitting it as a radio wave, and an envelope signal that detects the modulated wave and uses the envelope of the modulated wave as a signal. The detection unit 6 that outputs, the control unit 32 that outputs the control signal that minimizes the amplitude fluctuation of the envelope signal to the signal processing unit 3 based on the envelope signal from the detection unit 6, the quadrature modulation unit 7, and the output unit. 5, and a demultiplexing unit 4 that appropriately demultiplexes the modulated wave output from the quadrature modulation unit 7 into the output unit 5 and the detection unit 6.

The signal processing unit 3 is an A / D converter 20 for converting information such as voice and data into digital data, and a digital signal processor (DSP) for receiving digital data and performing arithmetic processing according to a predetermined modulation method. ) Processing unit 21, D / A converter 22 for analogizing the digital signal modulated by the DSP processing unit 21 to generate I and Q signals, and low-pass filter (LPF) 23 for removing unnecessary signals in I and Q signals. It has (23a, 23b).

The quadrature modulator 7 receives a carrier wave oscillator 19 for generating a carrier wave signal, the I and Q signals from which unnecessary signals are removed from the signal processor 3, and a carrier wave from the carrier wave oscillator 19 to generate a modulated wave. It has a quadrature modulator 24 for generation.

The demultiplexing unit 4 is composed of a coupler (switching means) 25, and demultiplexes the modulated wave input from the quadrature modulator 24 into the output unit 5 and the detection unit 6.

The output unit 5 includes a power amplifier 27 that amplifies the modulated wave input from the demultiplexing unit 4, and a bandpass filter (BP) that limits unnecessary radiation of the signal amplified by the power amplifier 27.
F) 28 and an antenna 29 through which the signal from the BPF 28 is radiated as a radio wave.

The detector 6 detects the modulated wave from the demultiplexer 4 and outputs an envelope signal, and digitizes the analog envelope signal from the detector 30.
It has a / D converter 31.

Then, the digitized envelope signal from the detector 6 is detected and the A / D converter 2 of the signal processor 3 is detected.
0, the DSP processing unit 21, and the control unit 32 for controlling the D / A converter 22.

The operation of the first embodiment will be described in more detail. When the modulated wave based on the I and Q signals whose amplitudes are unbalanced is detected by the detector 30, an envelope signal whose amplitude periodically changes can be obtained. Therefore, by minimizing the amplitude of the envelope signal, it is possible to deal with the distortion of the modulated wave when the amplitudes of the I and Q signals are unbalanced.

This envelope signal is I, as shown in FIG.
Since there is a pole (minimum point) with respect to the amplitude change of the Q signal, the point where the amplitude fluctuation of the envelope signal becomes the smallest can be obtained by a simple gradient method.

By the way, the amplitudes of the I and Q signals can be easily changed by changing the calculation parameters in the DSP processing section 21. Therefore, the control unit 32 outputs an amplitude balance control signal (distortion correction signal) to the DSP processing unit 21 based on the envelope signal from the A / D converter 31 so that the amplitude of the envelope signal is minimized. , Either one or both of the amplitudes of the Q signals are changed. This gives I,
It is possible to minimize the distortion of the modulation wave caused by the imbalance in the amplitude of the Q signal.

Similarly, the distortion of the modulated wave when there is a carrier leak can be minimized. This will be described with reference to FIG. In Fig. 9 (a), the Q signal is 1/3 in the Q-axis direction.
The signal point diagram when there is a carrier leak that shifts is shown. At this time, if the signal points are modulated by the I and Q signals that go around the signal circle, a modulated wave whose amplitude fluctuates in synchronization with rotation as shown in FIG. 9B is obtained. Therefore, if this modulated wave is detected by the wave detector 30 to minimize the amplitude of the envelope signal, it means that the carrier leak is corrected as a result.

By the way, in order to minimize the carrier leak, it is necessary to minimize the carrier feedthrough generated in the multiplier (see FIG. 5) in the quadrature modulator 24. In the actual quadrature modulator 24, four I signal, I bar signal, Q signal, and Q signal from the DSP processing unit 21 are used.
A baseband signal composed of signals is input in a differential format. Carrier feedthrough is minimized by varying the DC offset of the bar I signal with respect to the I signal, as well as Q.
It is minimized by varying the DC offset of the Bar Q signal with respect to the signal.

At this time, the I signal and the Q signal are independent signals, and the envelope signal when the DC offset of the bar I signal or the bar Q signal is changed has a pole point as shown in FIG. Therefore, carrier leakage can be minimized by independently adjusting the DC offset. That is, the distortion of the modulated wave can be improved.

For example, the I signal is fixed and the DC offset of the bar I signal is changed so that the amplitude of the envelope signal is minimized. Then, the Q signal is fixed and the DC offset of the bar Q signal is changed to re-envelope. Set so that the amplitude of the line signal is minimized. This DC offset adjustment is performed by the detection unit 6
This can be easily performed by the control unit 32 outputting the DC offset balance control signal (distortion correction signal) to the DSP processing unit 21 so as to minimize the amplitude of the envelope signal based on the information from (1).

Further, the 90-degree phase shifter can similarly improve the distortion of the modulated wave when the carrier phase is not completely orthogonal. In this case, the ideal modulated wave S (t)
Can be written as S (t) = I (t) cos (ωct) -Q (t) sin (ωct). The modulated wave S '(t) when the orthogonality of the carrier deviates by φ in this state is S' (t) = I (t) cos (ωct) -Q (t) sin (ωct + φ) = (I (t) -Q (t) sin φ) cos (ωct) -Q (t) cos φsin (ωct) = I '(t) cos (ωct) -Q' (t) sin (ωct)… Equation 2 where I '(t) = I (t) -Q (t) sinφ; Q' (t) = Q (t) cosφ. Therefore, in order to bring the modulated wave S '(t) shown in Formula 2 closer to the ideal signal shown in Formula (1), i (t) = I' (t) + Q (t) sin φ ... Formula 3 q (t) = Q '(t) / cos φ ... The correction calculation represented by Expression 4 may be performed. That is, the control unit 32 outputs the orthogonality control signal (distortion correction signal) to cause the DSP processing unit 21 to output the i and q signals given by the equations 3 and 4. At this time, the control unit 32 changes φ so that the amplitude fluctuation of the envelope signal becomes small. Then, the distortion is corrected by using the i and q signals at the time of the minimum as the I and Q signals.

FIG. 11 shows a procedure for correcting various kinds of distortion by the above distortion correction signal. When performing distortion correction, first set parameters (S
1). It is also possible to set in advance. The contents of the parameters will be explained each time.

Next, the contents of distortion correction are designated (S
2). For example, “1” is input when performing amplitude unbalance correction, “2” is input when performing offset correction, and “3” is input when performing orthogonality correction.

As a result, the DSP controller 21 outputs a baseband signal (test signal), and the quadrature modulator 7 outputs a modulated wave (S3). The detection unit 6 detects this, detects the amplitude fluctuation of the envelope signal, and the control unit 32 detects the maximum value of the amplitude fluctuation of the envelope signal and stores it in the variable A (S).
4).

Then, the control unit 32 controls the DS according to the correction item.
A distortion correction signal is output to the P control unit. The content of the distortion correction signal at this time is, for example, I in the case of the amplitude balance control signal.
It is a signal that increases the amplitude of the signal by (F × M1).
“F” is “± 1”, which is “1” by default. Therefore, when F = 1, the amplitude of the test signal increases by M1 and when F = -1, it decreases by M1. The same applies to the DC offset balance control signal and the orthogonality control signal (S5).

As a result, the DSP controller 21 changes and outputs the test signal (S6). The detection section 6 detects the modulated wave at this time, and the control section 32 detects the maximum value of the amplitude fluctuation of the envelope signal and stores it in the variable B (S7). Then, a difference [AB] between the maximum value of the amplitude fluctuation of the envelope signal before correction stored in the variable A and the maximum value of the amplitude fluctuation of the envelope signal after correction stored in the variable B is determined. Do (S
8). If the difference is negative [A−B <0], it indicates that the amplitude variation of the envelope signal is larger due to the correction, so “F” is set to “−1” (S9). , Return to step 4. On the other hand, when the difference is positive [A−B <0],
In step 10, it is determined whether the maximum value of the amplitude fluctuation of the envelope signal after correction is larger than a preset allowable value [D]. If larger [B> D], step 5
Then, the correction is repeated, and if small [B <D], the process proceeds to step 11 and the correction is completed.

Although one test signal (baseband signal) has been described in the above description, it is actually carried out for two baseband signals of I and Q signals, which are sequentially carried out. That is, the above correction is performed on the I signal, and then the above correction is performed on the Q signal. Further, the case where the amplitude imbalance correction, the offset correction, and the orthogonality correction are selected and described has been described, but these may be sequentially performed.

As described above, according to the first embodiment, the detection unit 6 is provided and the control unit 32 controls the DSP processing unit so as to minimize the amplitude of the envelope signal of the I and Q signals. By adjusting the amplitude of the baseband signal, it is possible to correct the distortion of the modulated wave caused by various causes.

<Second Embodiment of the Second Invention> A second embodiment of the second invention will be described with reference to FIG. The transmitting apparatus 2 according to the second embodiment performs signal processing on transmission information by digital signals and outputs analog I and Q signals.
A quadrature modulator 7 that multiplies signals and Q signals by mutually orthogonal carriers and outputs a modulated wave, an output unit 5 that amplifies the modulated wave and emits it as a radio wave, and detects the modulated wave and performs the modulation. A detection unit 6 that outputs an envelope signal whose signal is the envelope of the wave, and outputs a control signal that minimizes the amplitude fluctuation of the envelope signal to the signal processing unit 3 based on the envelope signal from the detection unit 6. The control section 32, which is provided between the quadrature modulation section 7 and the output section 5, outputs the modulation wave output from the quadrature modulation section 7 to the detection section 6 when the distortion of the modulation wave is corrected, and the output section during communication. 5 and a demultiplexing unit 4 for outputting to 5 The same parts as those of the first embodiment of the first invention are designated by the same reference numerals and the description thereof will be omitted.

The demultiplexing section 4 has output terminals 35a and 35b, and an RF switch (switching means) 35 for allocating the modulated wave input from the quadrature modulator 24 to the output section 5 and the detection section 6, and from the output terminal 35a. An output driver amplifier (pre-stage amplifier) 36 that amplifies an input modulated wave, an output BPF (filter means) 37 that limits a band of a signal from the output driver amplifier 36, and a detection driver that is input from an output terminal 35b. It has an amplifier (pre-stage amplifier) 38.

The RF switch 35 and the detection driver amplifier 38 are controlled by the controller 32, and the output terminal 3
When 5a is selected, it is in a communication state, and when the output terminal 35b is selected, it is in a distortion correction state of a modulated wave.

Since it is sufficient to perform the distortion correction of the modulated wave once, the output terminal 35b is selected and the distortion correction is performed, for example, when the power is turned on, and otherwise the output terminal 35 is used.
ba can be selected and put into a communication state. That is, the RF switch 35 is switched to the detection unit 6 side so as to generate the envelope signal only at the time of distortion correction, and the detection driver 3 is used.
Turn “8” on.

The detection driver amplifier 38 amplifies the modulated wave to a level sufficient to detect the envelope signal. In the amplification at this time, since the resolution of the A / D converter 31 is usually about 20 mV, the output signal from the detector 30 is several V
If so, the amplitude of the envelope signal can be corrected with an accuracy of about 1%. Therefore, the detection driver amplifier 38
Is amplifying the modulated wave to meet this requirement.

After the output driver amplifier 36 amplifies the signal to a predetermined level, the output BPF 37 limits unnecessary radio waves other than the radio waves specified by the transmitter. When the minute signal is amplified to the final level at once by the amplifier such as the power amplifier 27, the unnecessary signal is also amplified at the same level. Generally, such an unnecessary signal is provided in the final stage B.
Although the filtering is performed by the PF 28, if it is amplified at one time, the level to be filtered has a width, and the filtering cannot be performed accurately. Therefore, as described above, the output driver amplifier 36 amplifies the power amplifier 27 to a predetermined level before the power amplifier 27, and outputs the output BP.
The unnecessary signal is once removed by F37. This relaxes the filtering accuracy required for the BPF 28.

In the above description, the case where the distortion of the modulated wave is corrected immediately after the power is turned on has been described.
Is not limited by such limitations.

As described above, since the modulated wave is output to the detection section 6 only when the distortion of the modulated wave is corrected, the I and Q signals are transmitted during communication.
There is no need to adjust the signal amplitude or the like. Further, since unnecessary signals are removed in advance before inputting to the output unit, the BPF 28
No need for high filtering accuracy. In addition, the modulated wave is amplified and input to the detection unit 6, so that the distortion of the modulated wave can be corrected with high accuracy.

<Third Embodiment of the Second Invention> A third embodiment of the second invention will be described with reference to FIG. The transmitting device 2 according to the third embodiment processes the transmission information by a digital signal to output analog I and Q signals.
A quadrature modulator 7 that multiplies signals and Q signals by mutually orthogonal carriers and outputs a modulated wave, an output unit 5 that amplifies the modulated wave and emits it as a radio wave, and detects the modulated wave and performs the modulation. A detection unit 6 that outputs an envelope signal whose signal is the envelope of the wave, and outputs a control signal that minimizes the amplitude fluctuation of the envelope signal to the signal processing unit 3 based on the envelope signal from the detection unit 6. The control section 32, which is provided between the quadrature modulation section 7 and the output section 5, outputs the modulation wave output from the quadrature modulation section 7 to the detection section 6 when the distortion of the modulation wave is corrected, and the output section during communication. 5 and a demultiplexing unit 4 for outputting to 5

The demultiplexing unit 4 according to the third embodiment includes a driver amplifier (previous stage amplifier) 39, an RF switch (switching means) 35, and a BPF (filter means) 37. The same parts as those of the first and second embodiments of the second invention are designated by the same reference numerals and the description thereof will be omitted.

In the demultiplexing unit 4 of the second embodiment, the output driver amplifier 36 is provided on the output unit 5 side, and the detection driver amplifier 38 is provided on the detection unit 6 side.
This was intended to amplify the modulated wave output from the quadrature modulator 24 to a predetermined level. Therefore, the second embodiment
Then, the driver amplifier 39 that also functions as the output driver amplifier 36 and the detection driver amplifier 38 is provided in the preceding stage of the RF switch 35 to reduce the number of required driver amplifiers.

That is, when the modulated wave from the quadrature modulator 24 is input to the demultiplexing unit 4, it is first input to the driver amplifier 39, amplified to a predetermined level, and then distributed to the output unit 5 and the detection unit 6. When the output terminal 35a is selected and the modulated wave is output to the output unit 5, the signal has already been amplified to a predetermined level, so that the signal is output via the output BPF 37 as described in the second embodiment. Get better

As described above, the configuration of the demultiplexing unit 4 can be simplified by providing the driver amplifier 39 before the RF switching unit 35.

<Fourth Embodiment of the Second Invention> A fourth embodiment of the second invention will be described with reference to FIG. The transmitting apparatus 2 according to the fourth embodiment performs signal processing on transmission information as a digital signal and outputs analog I and Q signals.
A quadrature modulator 7 that multiplies signals and Q signals by mutually orthogonal carriers and outputs a modulated wave, an output unit 5 that amplifies the modulated wave and emits it as a radio wave, and detects the modulated wave and performs the modulation. A detection unit 6 that outputs an envelope signal whose signal is the envelope of the wave, and outputs a control signal that minimizes the amplitude fluctuation of the envelope signal to the signal processing unit 3 based on the envelope signal from the detection unit 6. The control section 32, which is provided between the quadrature modulation section 7 and the output section 5, outputs the modulation wave output from the quadrature modulation section 7 to the detection section 6 when the distortion of the modulation wave is corrected, and the output section during communication. 5 and a demultiplexing unit 4 for outputting to 5

The demultiplexing unit 4 according to the fourth embodiment has a driver amplifier 39, an output BPF 37, and a detection BPF (filter means) 40. The first embodiment of the second invention
3 to 3, the same parts are designated by the same reference numerals, and the description thereof will be omitted.

The modulated wave input from the quadrature modulator 24 is first amplified by the driver amplifier 39 and then output BPF3.
7 and the BPF 40 for detection. At this time B for detection
The PF 40 is set to a frequency band outside the frequency band permitted by the transmitter, that is, a frequency band through which signals of the stop band frequency in the output BPF 37 and the BPF 28 pass. As a result, the output BPF 37 and BPF 2
In 8, only the signal whose output is limited is the BPF 40 for detection.
Will pass through.

In general, the carrier oscillator 19 is composed of a frequency synthesizer, so that a carrier having a frequency band other than the base band can be easily generated. In addition, the quadrature modulator 24 and the driver amplifier 39 also have a relatively wide band. Therefore, when correcting the distortion of the carrier wave, a carrier wave outside the transmission band is also generated, and the carrier wave outside the transmission band is selectively detected by the detection BPF 40 to detect the envelope signal.

At this time, the output of the driver amplifier 39 is sufficiently attenuated because it is in the stop band of the output BPF 37 and the BPF 28, and the power amplifier 27 at this time is turned off so that it is not allowed by the transmitter. The distortion of the quadrature modulator 24 can be corrected while preventing the emission of unnecessary radio waves.

As described above, the detection BPF 40
Is set to pass a signal in a frequency band outside the frequency band allowed by the transmitter, so the distortion correction accuracy of the modulated wave can be set by setting the frequency at which the distortion of the modulated wave becomes the most prominent. Can be improved.

Further, when the distortion of the modulated wave is corrected, the emission of the radio wave is stopped. Therefore, if the transmission device emits the radio wave of a frequency other than the designated frequency, it will be forbidden because it interferes with other devices. The transmitter according to the present embodiment has an advantage that distortion of a modulated wave can be corrected without radiating unnecessary radio waves.

In the above-mentioned first to fourth embodiments, the transmission frequency is directly generated by the carrier oscillator 19. But Figure 1
As shown in FIG. 5 (a), the frequency of the carrier wave generated by the carrier wave oscillator 19 is set to a low frequency, the frequency is modulated at the frequency, and then the frequency is modulated by the local oscillator 41 to obtain the required transmission frequency. Generates the frequency of mixer 4
The frequency modulation may be performed by mixing with 0.

Further, as shown in FIG. 15B, a carrier wave is generated by the carrier wave oscillator 19, and the carrier wave is mixed with the signal transmitted from the local oscillator 43 by the mixer 42 to obtain the quadrature modulator 2.
It may be the final carrier wave to 4.

Also, in North American cellular automobiles and the like, FM modulated data of 10 kbps is transmitted at the time of system access such as call origination and call termination. By using this, the signal itself permitted by the system is used to distort. It is also possible to make a correction.

[0077]

According to the first aspect of the present invention, when the distortion of the modulated wave is corrected, a constant envelope is generated in the modulated wave based on the pair of baseband signals, and this modulated wave is subjected to envelope detection. Since the envelope signal is obtained, and the distortion of the modulated wave is corrected by feeding back information so as to minimize the amplitude fluctuation of the signal, it is possible to easily and accurately correct the distortion of the modulated wave. .

According to the second aspect of the invention, the detection section detects the modulated wave to obtain an envelope signal, and the amplitude fluctuation of the envelope signal is minimized to control the amplitude imbalance of the pair of baseband signals. An amplitude balance control signal, an orthogonality control signal that controls the amplitude of each baseband signal so as to be equivalent to a modulated wave when the phase difference between the two carriers is 90 degrees, and one of a pair of baseband signals The control unit outputs the distortion correction signal including at least one of the DC offset balance control signals for controlling the DC offset value to the DS.
The distortion of the modulated wave can be easily corrected by outputting to the P processing unit and correcting the baseband signal.

[Brief description of drawings]

FIG. 1 is a block diagram of a transmission device applied to an explanation of a first embodiment of a second invention.

FIG. 2 is a partial block diagram of a conventional transmitter.

FIG. 3 is a block diagram of a quadrature modulator.

FIG. 4 is an explanatory diagram of a signal point diagram.

FIG. 5 is a circuit diagram of a general multiplier.

6A and 6B are signal point diagrams for explaining distortion of a modulated wave, where FIG. 6A is an ideal signal point diagram, FIG. 6B is a signal point diagram when a quadrature modulator has a carrier leak, and FIG. Signal point diagram when there is an imbalance in the amplitude of the Q signal (I signal <Q signal), (d) 9
It is a signal point diagram when the phase of the carrier wave by a 0 degree phase shift converter is not orthogonalized correctly.

7A and 7B are diagrams illustrating a method of distorting a modulated wave applied to the description of the first and second embodiments of the present invention, in which FIG. 7A is a signal point diagram at the time of non-modulation, and FIG. Signal point diagram when rotating at a constant speed, (c) is a signal point diagram when there is an imbalance in the amplitude of the I signal or Q signal, and (d) is a diagram showing the time change of the amplitude in the case of (c). Is.

FIG. 8 is a diagram showing changes in the amplitude of the envelope signal with respect to the amplitude of the I signal or the Q signal.

9A and 9B are explanatory diagrams in the case where there is a carrier leak, FIG. 9A is a signal point diagram, and FIG. 9B is a diagram showing a change in amplitude of a modulated wave.

FIG. 10 is a diagram showing the amplitude of an envelope signal with respect to a DC offset value.

FIG. 11 is a diagram showing a procedure for correcting various types of distortion with a distortion correction signal.

FIG. 12 is a block diagram of a transmission device applied to the description of the second embodiment of the second invention.

FIG. 13 is a block diagram of a transmission device applied to the description of the third embodiment of the second invention.

FIG. 14 is a block diagram of a transmission device applied to the description of Embodiment 4 of the second invention.

FIG. 15 is a block diagram of a transmission device applied to an explanation of another embodiment of the second invention.

[Explanation of symbols]

 2 wireless transmitter 3 signal processor 4 demultiplexer 5 output 6 detection 6 quadrature modulator 25 combiner (switching means) 32 controller 35 RF switcher (switching means) 36 driver amplifier (pre-stage amplifier) 37 Output BPF (filter means) 38 Detection driver amplifier (pre-stage amplifier) 39 Driver amplifier (pre-stage amplifier) 40 Detection BPF (filter means)

Claims (8)

[Claims] 1. Distortion of a modulation wave generated by digitally processing transmission information to output a pair of baseband signals, multiplying each of two orthogonal carrier waves by each baseband signal, and then adding them. In the method of correcting distortion of a modulated wave, the distortion of the modulated wave is corrected, a constant envelope is generated in the modulated wave based on the pair of baseband signals, and the modulated wave is subjected to envelope detection. A method for correcting distortion of a modulated wave, comprising: obtaining an envelope signal and correcting at least one baseband signal so as to minimize amplitude fluctuation of the envelope signal. 2. A signal processing unit for digitally processing transmission information to output a pair of baseband signals, and a baseband signal multiplied by each of two orthogonal carrier waves and added to output a modulated wave. In the transmission device having a quadrature modulation unit, a detection unit for performing envelope detection of a modulation wave formed based on the pair of baseband signals that generates a constant envelope for the modulation wave, and a detection unit from the detection unit. A distortion correction signal to the signal processing unit based on the envelope signal to correct at least one baseband signal so as to minimize the amplitude fluctuation of the envelope signal. Transmitter. 3. The distortion correction signal output from the controller is
The transmission device according to claim 2, wherein the transmission device is an amplitude balance control signal that compensates for an unbalance in amplitude of a pair of baseband signals. 4. The distortion correction signal output from the controller is
The transmitter according to claim 2, wherein the transmitter is an orthogonality control signal that controls the amplitude and phase of at least one baseband signal so as to compensate for the orthogonal shift between the two carriers. 5. The distortion correction signal output from the controller is
The transmitter according to any one of claims 2 to 4, which is a DC level balance control signal for compensating for an imbalance of DC levels of paired baseband signals. 6. A demultiplexing unit that demultiplexes a part of the modulated wave output from the quadrature modulation unit to the detection unit, or distributes and outputs the modulated wave to the detection unit when distortion of the modulated wave is corrected. The transmission device according to claim 2. 7. The transmitter according to claim 6, wherein the demultiplexing unit has a pre-stage amplifier that amplifies the modulated wave to a predetermined level when the modulated wave is demultiplexed or distributed and output. 8. The transmission device according to claim 6, wherein the demultiplexing unit has a filter unit that removes an unnecessary signal in the modulated wave.